基于网格搜索-牛顿迭代法的微震震源定位算法

Micro-seismic event location based on Newton iteration method and grid-search method

利用最优化算法对微震定位进行求解时,为了保证全局且快速收敛,结合网格搜索法的全局收敛性和牛顿迭代法的快速准确性,提出一种基于网格搜索-牛顿迭代法的微震震源定位反演算法。新算法首先通过对监测区域进行稀疏的网格划分,利用网格搜索法得到初步的定位结果,再以此结果作为牛顿迭代法的初始迭代值进行准确的定位计算。通过模拟实验,研究了地下介质速度各向异性和实际工程中测速误差对定位结果的影响,并与牛顿法、网格搜索法和模拟退火法对比新算法在定位准确度、稳定性以及计算效率方面的表现。结果表明:该算法在理论上可以相对高效、准确、稳定地定位微震事件。最后利用实例验证新算法定位效果,定位误差约为4 m。该算法在微震定位中具有一定的实用价值。

In order to make the optimization algorithm convergent globally and quickly when locating micro-seismic events,considering the good performance of grid-searching method on global convergence and advantages of Newton iteration method for calculation speed and accuracy,a location method based on grid-searching method and Newton iteration method is proposed.First an approximate location result is obtained by grid-seaching method with sparse discretized grids in the monitoring area and the result is the initial iteration value for Newton iteration method;second Newton method is applied for the accurate location result.The influences of anisotropy of the velocity model and velocity measure error are analyzed in simulation experiments and the proposed method is compared with Newton iteration method,grid-searching method and simulated annealing method about location accuracy,efficiency and stability.The location results show that the proposed method can locate microseismic events accurately,efficiently and stably.The proposed method is also tested with field data.The location result is less than 4 m.So the method is practical for microseismic event locations.